There's no point suffering in silence when it's natural to talk about how you're feeling.
Still, take care not to scare him off by laying everything out - just talk about the little things. For example, tell him it hurts you when he can't take his eyes off any leggy blonde he sees on the street, or when his eyes light up when he's talking about Little Miss Perfect at the office.
If he still doesn't get the message, try turning the tables on him. Ask him how he'd feel if you started admiring his best mate's fit bum or talking about how amazing your gorgeous new colleague is. That should get him thinking...